Poor performances can send shock waves through our system. Any of us who have played music for a long time can probably share multiple horror stories in regards to performances. The culprits range from things outside of our control to things we are directly responsible for. Either way, it usually feels horrible.
There are allegedly only so many hours in a day that students can set aside time to learn repertoire. Many teachers I speak with get flustered by the amount of time they spend trying to get one to a few pieces up to a student’s potential, knowing all along that the student needs to know far more repertoire than what they ever have time for in the lessons and in their practice.